Geotechnical engineering and the usage of geosynthetic materials are very common in today's civil engineering marketplace. One of the most common geosynthetic materials available today are drainage products. Drainage products are generally comprised of a geonet or a geonet combined with a filtration fabric which may be one of many varieties. These products are used for a broad variety of applications. Common applications include drainage/leachate collection layers in waste storage facilities, leak detection layers in waste storage facilities, the use of a geosynthetic drainage material for gas venting in water and wastewater storage and treatment facilities, the use of geosynthetic drainage layers in roadway, rail and transportation applications and many others. In all of these applications, there are generally two performance factors which determine the suitability of the drainage media. These performance factors are the transmissivity (flow capacity) of the drainage media and the maximum allowable overburden pressure which the drainage media can support and still perform the functions required of it.
Waste collection sites are, of course, one well known type of geotechnical construction site, and are unavoidably required in today's societal structures. Such sites can require large amounts of valuable land, particularly in urban areas where land is most in demand. Also, while desirable uses can be made of such lands (for example, golf courses have been built on such sites), such desirable uses typically have to wait until the land is no longer being used to collect further waste and the often high pile of waste has stabilized. While use and stabilization of such sites can take many years, there is nevertheless a desire to have that accomplished as quickly as possible, not only to increase the safety of those who might have to be at the site but also to allow for the desired use of others (for example, golfers) and to enhance the environment of those who live in the area as soon as is reasonably possible.
Toward that end, bioreactor landfills have been used to modify solid waste landfills by re-circulating and injecting leachate/liquid and air to enhance the consolidation of waste and reduce the time required for landfill stabilization. To accomplish this, generally horizontal flow of the leachate/liquid beneath the surface of the landfill is required. In some instances, vertical injection pipes and horizontal pipe fields have often been used to facilitate this leachate/liquid flow. With these structures, a liner is commonly provided at the bottom of the site, which liner may be used to trap leachate which has run through the collected waste above, with pipes in that area used to collect the leachate and draw it out for re-circulation by pumping it out and distributing/dispersing the leachate back into the upper portions of the waste site through, for example, perforated pipes and/or horizontal trenches.
Unfortunately, vertical injection pipes and horizontal pipe fields have been costly, time consuming to install and maintain, and not entirely effective for a number of reasons. U.S. Pat. No. 6,802,672 discloses an advantageous system which addresses such problems.
Moreover, geocomposites have heretofore been used with many different types of systems where it is desirable to provide for fluid flow below the surface of built up land masses. As shown in FIGS. 1-3, such prior art geocomposites 10 have, for example, included a geonet 12 having high density polyethylene (HDPE) longitudinal strands 14 in the form of a grid 16 (see FIG. 1), with geotextiles 18 (such as, e.g., nonwoven needlepunched geotextiles) secured to one or both sides of the geonet (see FIG. 3). The geonet strands 14 have been long and oblong in cross-section, and oriented with the long dimension in a generally vertical orientation (see FIGS. 2-3), whereby the strands 14 provide a height for the geonet 12 which serves to facilitate flow along the plane of the geocomposite. However, while the strands 14 are themselves substantially incompressible HDPE, it has been the experience in the industry that under higher loading (which occurs, e.g., under greater depths of fill and/or pressures above the geocomposite), the rate of fluid flow along the plane of the geocomposite may be substantially reduced to undesirably low levels, which reduced flow can significantly inhibit the desired benefits of, for example, fluid drainage or recirculation.
The present invention is directed toward overcoming one or more of the problems set forth above.